The invention relates to forming V-shaped grooves in board materials such as paperboard, chipboard and particle board and more particularly to a method and apparatus for groove folding such board materials to form structures, such as boxes.
In a desire to lower cost by using more plentiful materials, box makers and furniture makers are turning away from wood and the like in favor of composite board materials for forming both decorative and structural panels. It has been customary, in forming the four sides of a wooden box to join four panels together at their edges using a joint such as a butt joint or a dovetail joint. However, butt joints are relatively weak and dovetail joints involve manipulations which are detailed and therefore expensive. Dovetail joints require cutting or punching notches and projections in both ends of all boards, applying glue, fitting the interlocking notches and projections of the four panels together to form the sides of the box and blocking the four-sided structure in a rectangular shape until the glue sets. A further finishing operation to trim the projections may also be required. In addition to the cost of such an operation, the step of cutting or punching the notches and projections produces a large quantity of dust and small scrap material which must be collected and disposed of.
Boxes have also been made by routing grooves in flake board with a rotating routing tool. Flake board is a dense, hard material made of wood shavings and chips bonded into a board. Routing the flake board produces large quantities of dust which may present a health hazard to those working with this process.
Paper boxes or box-like structures of light weight paperboard or of corrugated paperboard may be fabricated by creasing a single piece of the board and folding the board along the crease lines which define the box corners. The fold or crease lines are produced by cutting partially through the material or by compressing grooves in the material. However, compression grooving is not effective to define corners on all thicknesses of solid paperboard or particle board. As board thickness increases, the stiffness of the board and its limited receptivity to creasing causes the board fibers at the outer radii of the corners to crack and break due to tension in the fibers. Even at lesser thicknesses, corners formed by compression grooving and folding are often unsatisfactory since they are rounded and not sharply defined.
In order to bend thicker paperboard to produce reasonably square corners, a process known as step grooving has been used. Step grooving consists of removing a first relatively wide and shallow rectangular strip of material and then removing a relatively narrow and deep rectangular strip of material from the center of the wide and shallow groove. The paperboard is then folded along the line thus defined.
However, step grooving has several disadvantages. Step grooving requires two grooves and produces a large amount of scrap. Also, the resulting grooves are generally ragged since shreds of paper fibers are attached to the walls of the grooves. In addition, the opposed edges of the step grooves abut in an irregular fashion when they are folded to form a corner. Furthermore, the outside edges of the corners so formed are not sharply defined.